RT is classified as preoperative, definitive (without surgery) or adjuvant – postoperative.
In retroperitoneal sarcomas, a large volume is usually irradiated in both preoperative and postoperative indications. Tumor dimensions usually exceed 10 cm. Lesions often press on the organs of the abdominal cavity and retroperitoneum – liver, kidneys, duodenum, small and large intestine. The dosimetric advantage is significant in both indications. Another aspect is dose escalation. The benefit of dose escalation has been demonstrated. Doses above 55 – 57.5 GyE reduce the risk of local recurrence. In all high-risk organs, PRT significantly reduces the dose burden. The first clinical results are described in large retroperitoneal sarcomas. With preoperative irradiation up to 50 GyE in combination with intraoperative irradiation up to 11 GyE, a three-year recurrence-free survival of up to 90% is achieved in primary tumors. The results are more important as a “feasibility study” with favorable dosimetric parameters in PRT. CIRT, which has been used predominantly in Japan for more than 20 years, also has favorable results. In 24 patients with extensive inoperable soft tissue sarcomas, the retroperitoneum (median at 525 ccm) at doses of 52.8 – 73.6 GyE (median 70.4 GyE) in sixteen fractions, reaches LC 69% in five years and survival 50% in five years. Toxicity does not exceed G2.
Especially in the area of the girdle, significantly higher homogeneity of irradiation of the target volume and lower skeletal dose load can be seen with PRT. A lower risk of pathological bone fractures is derived from the reduction of the dose burden. The question of safe dose escalation is also relevant for limb sarcomas. With regard to the permanent risk of local recurrences in limb sarcomas, PRT dosimetry also provides greater opportunities for possible subsequent re-radiation.
RT has an irreplaceable role in the treatment of chordomas and chondrosarcomas, in addition to surgery. However, the effectiveness of RT is conditioned by high doses of up to 80 GyE. With local aggressiveness and low metastatic potential, the main parameters are LC efficacy and overall survival. The need for dose escalation (usually in the axial placement of the lesion) is required by special RT techniques and leaves room for PRT.
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